Photoelectric tube system



Oct. 26, 1937.

P. L. SPENCER PHOTOELEC'IRIC TUBE SYSTEM Original Filed Oct. 7, 1929 F IG.

INVENTOR PERCY L. SPENCER BY 54%; g5

AT TOR NEY\ Patented 26, 1937 UNITED STATES PATENT OFFICE 2,096,863" rno'roamcrarc TUBE SYSTEM Percy L. Spencer, West Newton, Mass., assignor to Raytheon Production Corporation, Newton, Mass, a corporationof Delaware Claim.

This invention relates to a photo-electric tube system. This application is a division of my copending application, Serial No. 397,881, filed October 7, 1929, in which the tube used in this sys- 5 tem is claimed. The invention generally relates to a device in which a gaseous discharge is initiated or stopped by the action of light. The invention finds its simple and most useful embodiment in the form of a tube having a glass or similar transparent envelope on the inside of which is formed a photoelectric coating. Mounted within the device is an anode of any shape whatsoever and a cathode of the ordinary type useful in glow discharges. Any suitable gas, preferably of the rare group, is introduced up to a pressure of about 2 mm.

The photo-electric coating and anodeare-preferably connected to a source of potential in the ordinary manner and under the same conditions as a photo-electric tube. The glow discharge cathode, however, is connected to the negative Under such conditions, upon the impingement of light on the photo-electric coating, the electron emission is sufilcient to ionize the gaseous region within the tube' and permit a discharge to pass between the glow discharge'cathode and anode. As is well known in such a glow discharge tube as I have shown, the ionization of the gas in the 85 tube upon thepassage of a discharge is quite copious, and is sufllcient to produce enough positive ions to substantially neutralize the space charge. Due to this fact, when a discharge is initiated, practically no control can be exerted d0 uponthe discharge merely by such a member emitting electrons as the photo-electric coating of my device.- light on the photo-electric coating would be of no avail whatever in reversing the process and de- 45 stroying the discharge. In order that'control may be eiflciently exercised in the reverse phase,

I preferably have a circuit so related to the tube as to result in oscillations being generated. In this way, with the use of direct current, the glow 50 discharge flickers while the light impinges upon the photo-electric coating.- As soon as the light is removed, the photo-electric coating fails to perform its function of aiding in starting up the tube. v

II A tube of this character may be used directly Therefore, the mere absence of bombardment.

A system ofthe above character may be very efi'ectively used to control and actuate alternating current relays to control powerful sources of energy. In this way the necessity for power- 10 fully amplifying the output of a photo-electric tube in order to make it available for relay purposes is entirely obviated.

Referring to the drawing, the figure. shows a tube partly broken away connected to a suitable system. I V 4 The photo-electric tube is preferably, though not necessarily, made as disclosed in my co-pending application, Serial No. 32l,472, filed November 23, 1928, which became Patent No. 1,991,774 20 on February 19, .1935. A'glass envelope l 'of any suitable shape is provided with a reentrant stem 2. Sealed in the stem 2 is a wire 3 terminating in a ring anode 4. This anode carries some lumps 5 of metallic magnesium. The tube is first thor- 25 .oughly exhausted. Anode I is suitably heated by high frequency induction means or the like so that the magnesium is-vaporized and caused to condense upon the interior surface of I. A window 6 may thereafter be outlined by local heatto ing, as by a hand torch. Thereafter the magnesium layer is oxidized and covered with a coating of photo-electric material. This may be effectively done by heating capsule I so that the chemicals therein interact. The chemicals are preferably the blchromate of the photo-electrically active metal, such as caesium, mixed with metallic silicon. After obtaining the layer of photo-elec trically active material, the envelope is filled with a rare gas, such as neon, helium or argon at a pressure of about 2 mm. or less. A wire 8 sealed in the wall of I terminates in a cap 9 to connect the photo-electric coating.

Supported by wires sealed in press 2 is a cylindrical'cathode I! of nickel or any other suitable material. One of the supports for this cathode terminates in a wire it. An ordinary vacuum tube base It may be cemented to the tube, and in such case wires 3 and II are soldered to two pins l6 and I! of the base. The remaining pins are 60 v dead. Capsule 'I may be supported by wire l'l welded to cathode l2. It should be noted that during the formation of the photo-electric active coating onthe interior surface of the glass wall asimilarcoating willalsobeformed onthesursistance 2! of about 100,000 ohms to the positive pole of a suitable source of current. Cathode i2 is connected through an alternating current relay 22 of the usual type to the negative pole of the battery. The photo-electric coating is suitably connected through a resistance 26 to the negative pole of a source of current and .which is shown here as an intermediate cell of the battery. The voltage across anode 4 and cathode H, as well as the photo-electric coating, may very easily be determined by experiment. Resistance 24 is preferably of the order of 2 to 10 megohms. This resistance is to prevent any considerable current from passing through the photo-electric coating. A condenser the device.

With the direct source of current shown, the tube when going will oscillate and tend to flicker.

In accordance with my present understanding of the theory of operation of the arrangement shown, this operation is produced in the following manner. The voltage from the battery which is impressed across the condenser 25 through the resistance 2! causes a charging current to flow through the resistance 2!, thus gradually raising the voltage across the condenser 25. The rate of charging is relatively slow due to the high resistance 2! which permits but a small current to flow. Since the voltage across the condenser 25 is impressed between the electrodes [2 and d, as this voltage builds up, it'

finally reaches a value suflicient to initiate a discharge between the electrodes i2 and 5 provided the photo-electric coating upon the inner surface of the tube is emitting electrons under the action of light radiations. 'If such electrons are not emitted, the voltage necessary to initiate a discharge between the electrodes i2 and d is greater than any potential which is reached across the condenser 25. However, as soon as a discharge is initiated between the electrcdes i2 and d, current from the condenser 25 flows through a discharge path including these two electrodes. Since this discharge path has substantially no impedance, condenser 25 is entirely discharged in a comparatively short period of time, and thus the voltage across the condenser 25 falls rapidly. When the voltage across the condenser 25 has fallen to a value which is insumcient to sustain the discharge between the electrodes 92 and d, the discharge will be extinguished; Since at this point the condenser '25 is substantially discharged, it is then ready to be charged again to the starting voltage of the discharge by the battery through the resistance it. Thus a series of charging current pulses will flow to the condenser 25 and such pulses will likewise manifest themselves in the entire circuit, including the condenser 25 which also includes the relay 22. When such current pulsations flow through the relay 22, it, being an alternating current relay, will operate so as tomove the armature connected with it, and thus control the circuit in which the contacts connected to that armature are placed. However, these pulses of current will flow through the relay 22 only if the tube is in conditionto periodically discharge the condenser 25. As, pointed out above, between each I discharge pulsation the current between the 25 is bridged directly across the cathode and anode of aoeaeegs The relay may control any desired mechanism.

The entire system is susceptible to many uses, such as the automatic opening of doors upon the .flashing of light, the control of devices in accordance with the time of the day, such as beacons in the ocean, etc.'

What is claimed is: v

1. A photo-electric system comprising a gaseous discharge device, said device comprising a gas-tight vessel containing a cathode, an anode, a gas filling at a pressure sufiicient to produce copiousionization upon the passage of a discharge between said cathode'and anode, and photo-electrically active meanselectrically separated from said cathode and anode and disposed adjacent the discharge path between said cathode and anode for emitting electrons into the discharge path between said cathode and anode whereby the starting voltage between said cathode and anode is decreased, means for impressing a periodically varying voltage across said cathode and anode, and means for energizing a load circuit in response to the current gas-tight vessel containing a cathode, an anode,

a gas filling at a pressure suflicient to produce copious ionization upon the passage of a discharge between said cathode and anode in the discharge path between them, and photo-electrically active means within said envelope and electrically separated from said cathode and anode, a cathode-anode circuit including means for impressing a periodically varying voltage across said cathodeand anode, and means for energizing a load circuit in response to the cur rent flowing between said cathode and anode through said discharge path, said photo-elec trically active means being connected to said cathode-anode circuit through a current-limiting impedance.

3. A photo-electric system comprising a gaseous discharge device, said device comprising a gastight vessel containing a cathode, an anode, a gas filling at a pressure suficient to produce copious ionization upon the passage of a discharge be tween said cathode and anode, and photo-electrically active means within said envelope and electrically separated from said cathode and anode, a cathode-anode circuit including means for impressing a voltage less than the normal starting voltage of a discharge between said cathode and anode but greater than the running voltage of such a discharge, said photo -electrically active means being connected to said cathode-anode circuit to lower the starting voltage between said cathode and anode to a value less than said voltage supplied between said cathode and anode when light radiations impinge on said photo-electrically active means.

4. A photo-electric system comprising a gaseous discharge device, said device comprising a gastight vessel containing a cathode, ananode, a gas filling at a pressure sufficient to produce copious ionization upon the passage of a discharge between said cathode and anode, and photo-electrically active means within said envelope and electrically separated from said cathode and an.

ode, a cathode-anode circuit including means for impressing a periodically varying voltage across said cathode and anode, and means for energizing a load circuit in response to the current flowing between said cathode and anode through said discharge path, said photo-electrically active means being connected to said cathode-anode circuit to lower the starting voltage of a discharge between said cathode and anode to a value less than said voltage supplied between said cathode and anode-when light radiations impinge on said photo-electrically active means.

5. A light-controlled system comprising a gaseous discharge device, said device comprising a glass vessel having a photo-electrically active material deposited on the inner surface thereof, a. filling of gas at a reduced pressure, an anode and a glow discharge cathode, a source of potential connected across the anode and cathode, an-

connected across from said anode to said cathode and photo-electrically active coating respectively,

. an alternating current relay in the anode glow discharge cathode circuit, and means for causing the glow discharge device to generate oscillations.

7. A light-controlled system comprising a glow discharge device, said device consisting of a glass vessel having its interior surface covered with oxidized magnesium, a photo-electrically active layer on said magnesium, a rare gas at a reduced pressure, an anode, a glow discharge cathode, a source of potential connected across said anode and photo-electrically active coating, means in said anode and photo-electrically active coating circuit for limiting the current, another source of potential connected across theanode and the glow discharge cathode, an alternating current relay in the anode-cathode circuit, and means comprising a condenser connected across,said anode and cathode for causing said device to generate oscillations.

8. A photo-electric system comprising a gaseous discharge device, said device comprising a gastight vessel containing a pair of electrodes, a gas filling at a pressure sufiicient to produce copious ionization upon the passage of a discharge between said electrodes, photo-electrically active means within said vessel and electrically sep arated from said electrodes, a circuit including a source of potential connecting said photo-electrically active means to one of said pair of electrodes, means for impressing a periodically varying voltage across said pair of electrodes, and means for energizing a load circuit in response to the current flowing between said pair of electrodes. I

9. A photo-electric system comprising a gaseous discharge device, said device comprising a gas-tight vessel containing a pair of electrodes, a gas filling at a pressuresufficient to produce copious ionization upon the passage of a discharge between said electrodes, photo-electrically active means within said vessel and electrically separated from said electrodes, a circuit including a source of potential and a current-limiting impedance connecting said photo-electrically active means to one of said pair of electrodes, means for impressing a periodically varying voltage across said pair of electrodes, and means for energizing a load circuit in response to the current flowing between said pair of electrodes.

10. A photo-electric system comprising a saneous discharge device, said device comprising a gas-tight vessel containing a pair of electrodes, a gas filling .at a pressure sufficient to produce copious ionization upon the passage of a discharge between said electrodes, means for impressing a voltage less than the normal starting voltage of a discharge between said electrodes but greater than the running voltage of such a discharge, and photo-electrically active means within said vessel and electrically separated from said electrodes, means for producing a discharge to said photo-electric means, which discharge produces ionization in said gas filling when said photo-electric means emits electrons in response to light radiations to lower the starting voltage of a discharge between said electrodes to a value less than said voltage supplied between said electrodes when light radiations impinge on said photo-electrically active means.

PERCY L. SPENCER. 

